A current comparator converts currents to voltages using load resistors in order to measure a difference between the currents flowing through the load resistors. When the resistance values of the load resistors are substantially the same, a difference between the converted voltages across the load resistors would be proportional to a difference between the currents flowing through the load resistors. As a result, by measuring the difference between the converted voltages, the difference between the currents can be accurately measured.
However, if a resistor mismatch (i.e., a difference between the resistance values of the load resistors) results from process variations in a fabrication process, a difference between the resistance values may dominate over the difference between the currents in determining the voltages across the load resistors. For example, if the resistance value of a first resistor is sufficiently greater than that of a second resistor, a first voltage across the first resistor may be higher than a second voltage across the second resistor, although a first current flowing through the first resistor is in fact lower than a second current flowing through the second resistor. In this case, the difference between the first and second currents may not be accurately measured by measuring the difference between the first and second voltages.
A conventional approach to address the above issues related to the resistor mismatch includes increasing a size of load resistors. For example, assuming substantially the same process variations in a fabrication process, if a first pair of matched resistors has a length and a width greater than a length and a width of a second pair of matched resistors, respectively, the first pair of matched resistors would have a smaller resistor mismatch than the second pair of matched resistors. However, this approach consumes a greater area for the matched resistors, and also may result in increased power consumption.